1. Field of the Invention
This invention relates generally to perpendicular magnetic recording write heads, and more particularly to a write head with a notched trailing shield for use in magnetic recording hard disk drives.
2. Description of the Related Art
Perpendicular magnetic recording, wherein the recorded bits are stored in a perpendicular or out-of-plane orientation in the recording layer, is a promising path toward ultra-high recording densities in magnetic recording hard disk drives. As shown in FIG. 1A, a “dual-layer” medium includes a perpendicular magnetic data recording layer (RL) on a “soft” or relatively low-coercivity magnetically permeable underlayer (SUL) formed on the disk substrate. This type of medium is shown with a single write pole (WP) type of recording head. A thin film coil (C) is shown in section between the WP and the return pole (RP) of the recording head. Write current through coil C induces a magnetic field (shown by dashed line 10) from the WP that passes through the RL (to magnetize the region of the RL beneath the WP), through the flux return path provided by the SUL, and back to the RP. The recording head is typically formed on an air-bearing slider that has its air-bearing surface (ABS) supported above the RL of the medium. In FIG. 1A, the medium moves past the recording head in the direction indicated by arrow 20. The RL is illustrated with perpendicularly recorded or magnetized regions, with adjacent regions having opposite magnetization directions, as represented by the arrows. The magnetic transitions between adjacent oppositely-directed magnetized regions are detectable by the read head (not shown) as the recorded bits.
FIG. 1A also shows a section of a trailing shield (TS) with a trailing shield notch (TSN) that is near the WP but spaced from the WP by a gap of nonmagnetic material. The use of a TS separated from the WP by a nonmagnetic gap slightly alters the angle of the write field and makes writing more efficient. The TSN causes a stronger magnetic field below the WP and sharper magnetic transitions written by the head, which is desirable. FIG. 1B is a view in the direction 1B-1B of FIG. 1A and illustrates the width of the WP to substantially define the trackwidth (TW) of the data recorded in the RL. The TS is substantially wider than the WP in the cross-track direction but the TSN portion is generally the same width as the WP. FIG. 2 is a perspective view showing the relationship between the WP, the TS with TSN, and the recording medium with the RL and SUL. As shown, the TSN is generally rectangularly shaped with a front edge 30 and generally parallel side edges 32, 34. FIG. 3 is a view of the slider ABS, as seen from the disk, and shows portions of the write head, with details of the WP, the TSN and the gap between the WP and the TSN. The WP has an end 40 generally parallel to the ABS and a trailing edge 42 that is generally orthogonal to the along-the-track direction and generally defines the TW. The gap typically includes alumina (Al2O3) as a result of the conventional fabrication process wherein the alumina is a “thin alumina mask” (TAM) formed over the layer of magnetic material used to form the WP. A resist is formed over the TAM and the structure is then ion milled to form the WP. After removal of the resist, the TAM remains above the WP. A thin film 50 of additional gap material, such as Ta or Rh, is deposited over the TAM, followed by electroplating of the magnetic material, typically NiFe, to form the generally rectangularly shaped TSN (with a front edge 30 and generally parallel side edges 32, 34) and the remainder of the TS.
The generally rectangularly shaped TSN can become saturated during writing. Additionally, the TAM that remains above the WP makes the gap layer thicker than necessary and thus makes the write field gradient less than optimal.
What is needed is a perpendicular magnetic recording write head with a trailing shield having an improved trailing shield notch and reduced-thickness gap between the write pole and the trailing shield notch.